1. Field of the Invention
A commonly used method for disinfection of soft contact lenses is to introduce the soft contact lens into a small holder containing a stabilized aqueous saline solution. The holder is introduced into a heater, where the holder and its contents are heated either by boiling water or a closed heated air environment. Temperatures of the solution in the holder generally range from about 70.degree.-90.degree. C and times for which the holder contents are maintained in this temperature range will generally vary from about 10-20 minutes. After cooling, the lenses may be removed from the holder, desirably rinsed and may then be introduced into the eye or left soaking, so as to remain hydrated over night.
While the disinfection method using an elevated temperature, frequently referred to as "boiling", is effective for disinfection, it has created a number of serious porblems for the soft contact lens wearer. Because of the chemical nature of the soft contact lens, a wide variety of materials will tenaciously adhere to the contact lens. Of particular importance are proteinaceous materials and lipid materials. The thermal treatment of the lens results in denaturation of the protein, which then forms a strongly adhering layer to the lens. Repetitive thermal disinfection of the contact lenses results in a continuous buildup of the proteinaceous layer, which also results in the binding of other materials, such as lipids, dust particles, and the like. As the proteinaceous layer builds up, the lens becomes irritating to the eye and with continued buildup loses its optical quality and clarity.
Any attempt to prevent the formation and buildup of a tenaciously adhering proteinacous layer during thermal disinfection is limited by a number of considerations. Among these considerations is the fact that the lens may be taken from the boiling solution and placed directly in the eye. Therefore, the solution must not introduce materials into the lens which will be irritating to the eye. Also, it is convenient that the boiling solution also be a rinse and soak solution, so that the lens after boiling may be rinsed with the same solution or be stored in the solution until used. Any additives introduced into the boiling solution must be stable and should not interact detrimentally with the contact lens. As a practical matter, the boiling solution must be stable and have a long shelf life, must be clear and must not adversely affect the optical characteristics and quality of the lens.
2. Description of the Prior Art
Reference is made to Applicant's copending application Ser. No. 651,744, filed Jan. 23, 1976.